Conventionally, a gyro sensor is known as a sensor for detecting an angular velocity, for example, as described in JP-A-2001-255153 corresponding to U.S. Pat. No. 6,443,008B. The gyro sensor includes a detector weight and a driver weight which oscillates parallel to a plane direction of a substrate. The driver weight and the detector weight are connected via a detector spring. Angular velocity detection is based on a detector weight oscillation in a direction perpendicular to the substrate plane by an angular velocity application with oscillation of the driver weight. The gyro sensor described in JP-A-2001-255153 includes a driver weight and a detector weight arranged on a disk form. The angular velocity is detected by oscillating the driver weight around a disk center when an angular velocity detection. Thus, the angular velocity is detected by getting a differential output derived from up and down oscillation of both sides of a disk which oscillates up and down perpendicular to a disk plane (a z-axis direction) like a seesaw by application of the angular velocity.
However, the gyro sensor in JP-A-2001-255153 may increase an output error when an impact in the z-axis direction is received. Specifically, the detector weights on both sides of the disk move in the z-axis direction when an impact in the z-axis direction is received. In cases where the detector weights on both sides move in a same mode of oscillation, an impact oscillation component in each operational output from the detector weights can be canceled by taking operational output. However, if the mode of oscillation is different from each other, the output error may increase. It is undesirable for the output error to be increase because the angular velocity cannot be detected precisely.